I run regularly, but when running today i felt a twisting/knot - like pain right below my belly button to the right. it's tender to touch.

Few possibilities: My guess is that it is an abdominal wall muscle strain, and it will resolve within a few days. Perhaps it will resolve after your next bowel movement. Some more serious internal disorders would be appendicitis, diverticulitis, twisting or volvulus of the intestine. If the pain is associated with fever, vomiting, diarrhea, very severe colicky pain, then obviously check with your doctor.